1. Field of the Invention
The present invention relates to a design support system such as CAD (computer aided design), and more particularly to an improvement in work efficiency.
2. Description of the Related Art
Recently, CAD generally performs modeling of figures by combining basic figure elements called primitives, or by performing predetermined processing of the primitives as they are, or a combination thereof. Specifically, when one edge of a cube is rounded to have a curved shape, a rounding process of that edge is performed with respect to a cube primitive to create a figure, or the same figure is created by extrusion processing of one quarter of a circle, for example.
As a conventional CAD system, there is known a CAD system which records a history of work contents such as creation, arrangement, processing, etc. of a primitive as work history data and also relates data (figure data) of a figure itself created by the work history data to record and manage as a file, as shown in FIG. 13. According to this CAD system, the work history data can be traced back to change the contents of the past work. For example, histories of design work for parts elements such as a bolt and a nut have their designs and structures made common to some degree and their shapes are simple. They can therefore be readily reused to design another product.
In an actual design situation, a design work of a single product is often conducted separately by a plurality of design teams at the same time in order to speed-up designing. Division of the design work is carefully decided to prevent the design results from individual teams from disagreeing with the designs made by other teams. However, it is difficult to completely eliminate mutually dependency. For example, to design a single vehicle body, a design of its outside body shape (designed surface, which will be hereinafter called a reference surface) and a design of each component part of each body section are separately performed by different teams, but the shapes of the body parts cannot be decided unless the outside body shape is decided because they must conform to the outside body shape.
For example, when the aforementioned conventional CAD system is used to design body parts of a vehicle, their designs and structures are variable depending on design targets, and their shapes are also complex, increasing work history data up to 3000 to 7000 steps. Therefore, it is not realistic to reuse the work history data in view of overhead costs for fetching a required shape from the work history data to know the meaning of work in each step etc. Consequently, design work has to be carried out again from the beginning, and this is very inefficient. It is difficult to reuse certain work history data to actually carry out design unless information such as, for example, directions of drawn line segments, input coordinate values and the like of the work are known even if that work history data is comprised of steps which happen to be reusable.
Meanwhile, when a history of each design work is to be recorded and a shape is represented with reference to a reference surface at a time when the design work is performed, e.g., by designating an offset amount from a temporary reference surface which is used as a standard, a shape conforming to the reference surface, even if it is changed, can be created with ease by reproducing the shape with an offset amount from the changed reference surface. However, if a number of surfaces, a direction of a boundary line or the like, which is referenced between the temporary reference surface and the changed reference surface, is changed, a conforming shape cannot be created properly.